Written by Jonathan Eisenthal
“You can adapt to change!” was the rallying cry issued to several hundred farmers who came to hear the latest science about nitrogen fertilizer.
Prof. Fabian Fernandez used these words to open the second annual Minnesota Nitrogen Management Conference last week in Rochester. The conference was titled, “Nitrogen: Minnesota’s Grand Challenge and Compelling Opportunity.”
A series of experts spoke through the day and took different angles at the issue of nitrogen, and all arrived at the same conclusion: farmers who adapt to the coming fertilizer limitation rules will come out ahead both in their crop yields and in their environmental stewardship results.
“Adjusting your nitrogen rate — keeping to the best management practices (BMPs) rates — is the single most important way to make a positive impact on the environment,” said Dr. Gyles Randall, emeritus, University of Minnesota Extension Service.
He described the indisputable findings of long-range studies conducted in Minnesota that showed the advisability of sticking to the BMPs. The studies have arrived at 120 lbs. per acre in many places, though there is regional variation.
He cited research that compared three different rates of nitrogen and two different timings: Fall applied 120 lbs. yielded 166, while putting on an extra forty pounds of ‘insurance fertilizer’ yielded only seven more bushels per acre. However, going to a split application in springtime, and using only 120 lbs. total again, the crop yield went up to 180 bushels.
“This is where you get the most bang for your buck,” Randall advises. “Spring applying according to the BMP rate.”
Fall-applied fertilizer tends not to stay in place, so it’s less effective. The main reason for this is climate change. University of Minnesota Extension climatologist and meteorologist Mark Seeley described how changes in temperature and precipitation are both working against the stability of fall applied fertilizer. The lack of a winter-long snow cover, the increased frequency of the freeze-thaw cycle throughout the winter and the increasing prevalence of thunderstorms that produce two-plus inches of rain (which inevitably erodes soil) all work to dissipate the fertilizer put down in the fall.
Randall and Prof. Jeff Vetsch, a University of Minnesota Extension Service soil scientist, provided solid evidence that going to applications that split fertilizer between a spring pre-plant and in-season applications, allowed farmers to save money by using only the BMP rate of fertilizer. At the same time, this boosts yields by assuring that the nutrients are in place when the plant needs them. And this reduces the risk of nutrient loss.
Prof. Ignacio Ciambatti, Kansas State University, made an indirect argument for in-season fertilizer applications by showing his research results that indicate modern hybrids take up more fertilizer after flowering than corn varieties planted by American farmers from the 1940s to 1990s. This finding may be key to understanding how modern hybrids tolerate higher plant populations, which is the key to higher yields.
The Minnesota Nitrogen Management Conference is organized by the University of Minnesota and the Minnesota Agricultural Water Resources Center (MAWRC). The U of M organized the first event in 2015, and this year started working with MAWRC to organize the event and the Nutrient Management Conference. The U of M and MAWRC worked together on both conferences to avoid overlap and use resources and planning committee members more effectively.
Presentations from the Nitrogen Management Conference can be viewed here.